Almost all cars available on the market today have some sort of power assist steering system arranged to assist a driver in steering steered wheels of the vehicle. Most car manufacturers have started to use Electrical Power Assist Systems (EPAS) in their vehicles, phasing out the formerly used Hydraulic Power Assist Systems (HPAS). The reason for doing so is weight savings, space savings and reduced manufacturing costs of EPAS compared to HPAS. In addition, electrical systems have an advantage in fuel efficiency because there is no belt-driven hydraulic pump constantly running, whether assistance is required or not. However, in general, an EPAS isolates more of the road contact feedback and therefore provides lower level of feedback of road information to the driver than an HPAS.
Some car manufacturers use steer-by-wire systems which provide steering control of a car with no mechanical components/linkages between the steering wheel and the wheels. Instead, control of the direction of the wheels is established through an electric motor, or motors, which are actuated by electronic control units monitoring steering wheel inputs from the driver using sensors. An inherent problem with a steer-by-wire system is that such systems need redundant elements to make them safe, since no mechanical connection is present between the steering wheel and the steered wheels. The cost of a steer-by-wire system is often greater than conventional systems due to greater complexity, development costs and the redundant elements needed to make the system safe. In addition, a steer-by-wire system has no natural road contact feedback to the driver so there is a need for artificial feedback to the driver from a dedicated force feedback motor.
In view of above, there is room for improvement concerning control of steering, feedback information to a driver, safety and manufacturing costs of a vehicle steering arrangement.